Generally the currents distributed in an electrical installation are controlled by electromechanical devices with the functions of circuit breaking, load and line checking and protection.
These electromechanical devices consists of fuses, relays, breakers, breakers with thermal or magnetical protection, contactors, voltmeters, ammeters and relevant similar units. They have normally great over-all dimensions and weights, and produce electromagnetic noise with the closing/opening of contacts.
These devices must be manually reset after their operation and are often subjected to problems caused by oxidation of the contacts.